Convert AAC to MP4 — Free Online Converter

AAC is the standard audio codec inside MP4 containers — they are natural partners defined together in the MPEG-4 specification. Converting a standalone AAC file to MP4 wraps the audio stream in the full MPEG-4 Part 14 container, adding proper metadata support, streaming headers, and compatibility with every video player, web browser, and mobile device on the planet. MP4 is the most universally supported media container in existence.

Raw AAC files (ADTS format) lack metadata, streaming optimization, and consistent player support. MP4 containers are recognized by literally every modern media device and platform. Wrapping AAC in MP4 enables web streaming with byte-range requests, proper metadata display in all players, and the ability to later mux video into the same container. Web browsers play MP4 audio natively via the HTML5 audio element.